Methods for monitoring a state variable of at least one battery cell of a battery as well as monitoring devices for this purpose are known in basic principle, so that a separate documentation of publications for this is not needed. Such battery cells or batteries are often employed in high-voltage battery systems, such as are used, for example, in electrically drivable motor vehicles or the like. At the present time, different quality inspections are carried out during the production of battery cells as well as of batteries assembled from them, such as, for example, an insulation measurement, a dielectric strength measurement, and/or the like. Beyond this, high-voltage battery systems often have an insulation monitoring device for active checking of the isolation or insulation of the high-voltage battery system. This device checks both a high-voltage plus connection terminal and a high-voltage minus connection terminal with respect to a ground of a device, such as, for example, the motor vehicle that comprises the high-voltage battery. When the high-voltage battery is employed in a motor vehicle, the insulation is monitored in relation to a motor vehicle ground.
Corresponding batteries that are formed from at least two battery cells are also known from the prior art.
A battery cell is a device that has two electrodes that interact electrochemically with each other. The interaction can occur with supplemental assisting action of an electrolyte. Battery cells, which are also referred to as galvanic cells, are preferably reversible in terms of their function, such as when they are utilized, for example, for batteries in the form of rechargeable batteries. On account of the electrochemical interaction of the electrodes, a direct current voltage that is specific to the battery cell chemistry is established at the electrodes and is supplied by way of connection terminal contacts of the respective battery cell that are connected to the electrodes.
This direct current voltage is, as a rule, relatively small. Many applications in electronics necessitate a direct current voltage that markedly exceeds the direct current voltage that can be supplied by a single battery cell. For this reason, a plurality of battery cells are often combined to form a battery and connected electrically inside the battery in accordance with the electrical requirements, for example, in the form of a series connection, a parallel connection, combinations thereof, or the like.
Inside the battery, the individual battery cells are therefore often connected to one another in an electrically conductive manner by means of bus bars or similar electrical conductors in the desired type of circuit, in order to be able to provide the desired direct current voltage at the connection terminal poles of the battery. Such batteries are employed, for example, as lead acid batteries in the motor vehicle sector, as nickel cadmium batteries in the aircraft sector, and, for interruption-free current supplies, as lithium ion batteries in the field of small household appliances and/or the like, but recently also in electrically driven vehicles.
Motor vehicles of the generic type are also well known. They preferably comprise motor vehicles that have an electrical system with a battery as well as a drive device connected to the electrical system. Such motor vehicles are, for example, electric vehicles, hybrid vehicles, in which a drive is possible both by means of an electric drive device and also by means of an internal combustion engine, or the like. In these vehicles, the battery and the drive device each have at least two electrical connection terminal contacts. For the purpose of the electrical coupling, at least one of the connection terminal contacts of the battery and one of the connection terminal contacts of the drive device are connected by means of an electrically conductive line to each other in an electrically conductive manner.
During the operation of battery cells or batteries of the generic type, problems can arise, particularly in regard to the intended operation, aging, and/or the like. This can be detrimental to the quality of the battery cells or of the battery.